Fuel injection system



Dcd. 29, 1959 T. M. BALL FUEL INJECTION SYSTEM Filed Aug. l5, 1958 2,918,914 .FUEL INJECTION SYSTEM vThomas yM. Ball, Bloomfield Hills, Mich., .assignor'to Chrysler Corporation, HighlandY Park, Mich., a 4corporation of Delaware Application August`13, 1958, Serial No. y'754,890 18 Claims. (Cl. 12S- 119) This invention relates to a fuel injection systenilfor 'use on internal combustion engines, -and in particular lre- 'lates "to an improved combination of fuelfeed -unit and i fuel injection nozzle, and an improved noz-zie.

In fuel injection systems it is customary to rmeter liquid fuel toffuel injection nozzles located on the 'intakeimani- -fold in juxtaposition to the engine cylinders. "These nozzles are comprised essentially ofres'trictions Vvin 'the'.-

conduits communicating with the manifold iwh'ich restrictions create-a pressure drop between said conduits and `the intake manifold to maintain sufficient "fuel pressure in said conduits to4 atomize the liquid fuell as it passes into the manifold. These restrictions'fha'velimited-utility, however, in that a low engine Vspeedswhen the liquid fuel pressure in the conduits is low and the `vacuurr'l in the 'intake manifold is high, this 'vacuum sucks enopg'hof the low vpressure liquid fuel from,thejgconduitsxtocause .a

vaporization o-f the fuel the-rein. The vaporthus'forrn'ed may occupy large spaced portions of the conduits'fand result in intermittent feeding of liquid fuel 'to `theeng'ine. This vapor may also result in a' lag 'in fuel feed response to sudden 'acceleration actuation due Lto the vapor spaces which ,must ll with liquid y'fuel before 'the acceleration boost fuel can flow to the engine.

The presentinvention obviat'es'these problems vbypro- 'viding'a means which is responsiveto manifold pressure 'to maintain a substantially ,constant and relativly-ihigh 'liquid fuel pressure in the conduits feeding thenozz'les over the entire speed range, of the engine-.1` 'high ,'.pressure is particularly effectivefatllow eng'in'efloadcon- "ditions 'to' preventvapor formatinginthe, conduits.

It is an object of this invention to provide Aa ,fu.el injection system .with an` improvedtype nozzlewhich -prevents vapor formation in thenozzlelfeed conduitst Another object is to providejanimprovedfuelinjeetion nozzle with. a variable area orifice and .a means to var .y 'fthe orifice according to intake manifoldpressure. Y

Another object is.to.provide,aspeedandload metering fuel injection system with amean's ,to preventupsetting ofitsnormal metering function dueto variationsin-intake manifold pressure.

Ln carrying out this --invention adiaphragm actuated metering needle is slidably .positioned in a nozzle body .member and is adapted to move `towardand away .from the fuel outlet end of thenozzlefeed .conduit which., is secured in the nozzle body. ThediaphragmV attached to the needle communicates -wit'hthe :manifold and-moves the needle toward the outlet end ofjthenozzlezfeedgconduit in response toa dropin.manifoldpressureu The movement of the diaphragmandneedleis calihratedwith respect to ymanifoldpressure byfmeans of a spring which allows the needle to restrict the flow..of fuel fromthe conduit at all Amanifold pressures an amountnecessary vtoIriaint-ain. suicientfuel pressure in theconduits4 to; pref vent fuel vaporization therein.

Qthenobjects. .and advantages will :become Yappar-'ent from the following deseriptionandfdrawings,rinywhch:

2,918,914 Patented Dec. 2v9,

ice

Figure 1 represents a'view partly in vcrosssectiot'r*offia complete fuel injection system; Figure 2 represents an enlarged view in'cross sectiono a nozzle of Fig. l; and

fFigure 3 represents a view in cross section of ain'o'zzle and pilot valve.

In Figure 1 is shown a fuel injection vsystem for an internal combustion engine designated generally `as 5 having separate cylinder banks 8, intake manifold conduits 88, eiihaust manifolds 7 and cylinders 9, said system'coinprising a fuel supply 10, a speed sensor 12, a load sensor 14, an accelerator pump 16, and fuel injection vnozzles 18; `'The speed sensor is provided with four housing por portion 20. connects chamber 34 with a lreturn flow con- VfluitjSt) which communicates with the inlet check 'valve- 52 of vaccelerator pump 16. A return fiow metering needie 5'6'having a tapered point 58 is secured 'to each of' said 'diaphragmsby suitable grommets 60.

V.A flyweight support 62vpivotally supports ilyweights 64" and@ and Ais secured to a flexibleshaftS 'which i s p eratively connected to the engine to/ rotate at a speeld directly proportional to `engine speed. Flyweightsvdlgand '66 'have projections 69 and 70 respectively thereon rch abut the end of needle 56 as .said .llyweightsp'ivot out-- wardly in response to rotation-off shaft 68k to ilrgeneedle .5 6 .toward orifice 48 against the force applied in theY opposite 'direction againstdiaphragm 28 .by the fuelllin chamber 34. l l' A ,conduit 72 'connects chamber 34 to the upstrein :chamber 74 of the load sensor which upstream chamber `communicates Witha .downstream fuel distribution ,chamber orrosette 7 6 of thefload sensoracro-ss a load meterin g ,oric'e '.78 .A load metering ,needle .80, -havingga Qreversely tapered yportion ;82-position in. orifice 78, is .operatively connected topisten 84reciprocably'mounted in, vcylinder f86 which cylinder. operatively .communicates with 'therlowpressure portions of each .intake .manifold ...8.8 `on `said [engine `through .conduit i9,0. yLow .pre Sure .orifice .78. llffplurality of -nozzle #feed conduits 59.4 ex- .tendvfrom chamber 'loof-fthe load -sensor-,toanfrequal rnur nber of .fuel injection vnozzles .-18tlocated'downstre'am of :the ithrottle valve 98 -in the intake manifold ,1 -Q9. `f

.Chamber 76 of the load sensor;is,connected to ychamber '36 yofthe 'speed sensor byconduitglvl() :toprovide anad- .justrnent ofthe return ilow Vrneteringneedle lwithfrespect .tor orifice 48 'based on ftheifpressjure differential-existe ing across orifice 78 of the load sensor., r 'f .An idle @boost I'conduit '-112.communicatesvitlrvsaid manifold 99 at a :point adjacent -thezed`ge lof'zthe :throttle valve 398 fand Y with the -fchamber' S8-fof Athe speed sensr. IAn air bleed yvalve 114 in conduity .f1-12 .is providedrto :regulate the pressure transmitted to-.-.chamber. 38 :from imanifold-9-9 duringidlingiofthe engine infoiderfto regu- .late .thereby the speed of the '.engine atidlin'g. Under v.rzgrnlalV .idling -conditonsthe pressure in chamber .as :is .lower .than in `chamber .40 `which isfvented-ztomtheeatrnostends to urge the needle 56 toward orifice 48 to retard the flow of return fuel therethrough and provide a sufficient fuel supply for idling. The requirement of this additional boost to needle 55 is due to the fact that at slow engine speeds the fiyweights are not flung outwardly with sufficient force to negate the frictional resistance of the needle 56 to movement.

The accelerator pump 16 having an inlet check valve 52 and an outlet check valve 116 receives fuel through said inlet valve into chamber 118 from which the return fuel continues through the return ow conduit 58 back to the tank. The depression of the accelerator will force piston 120 of said pump 54 downwardly to force fuel through check valve 116 and through conduit 122 directly to the downstream chamber 76 of the load sensorv The operation of the speed sensor 12 and load sensor 14 will be described separately from the fuel injection nozzle 18 and in relation to a change in static engine operating conditions, that is, constant engine speed and load. Under said static operating conditions, the combined forces exerted by flyweights 64 and 66 and the fuel in chamber 36 is balanced by the force exerted by the fuel in chamber 34 and the return flow member 56 is maintained stationary at a distance away from orifice 48. In this static condition, the amount of fuel delivered to the rosette 76 is constant and is equal to the constant amount of fuel being delivered to the system by the pump less the constant amount of fuel being returned to the fuel tank through the return fiow conduit 50. If this static condition represents the engine during normal driving speed, the pressure in chamber 40 has no noticeable effect on the operation of the unit and may be disregarded. It is only during idling and very low engine speeds that the pressure differential across diaphragm 32 becomes significant.

As the throttle valve 98 is moved to a more open position by the depression of the engine accelerator, an increase in manifold pressure is transmitted to the load sensor piston through conduit 9@ and moves said piston down to thereby move the load metering needle 80 to a more open position with respect to the load metering orifice 78. The pressure differential existing across said orifice is consequently decreased as more fuel is allowed to fiow into chamber 76. This decrease in pressure differential causes the flow through orifice 78 to deviate from the desirable flow which is substantially linear with respect to engine speed. To correct this condition and bring the pressure differential across said orifice up to a value where the ow of fuel therethrough is substantially linear to engine speed, the fuel pressure in speed chamber 34 and load sensor chamber 74 communicating therewith is increased. This increase in pressure is accomplished by moving the return flow metering member 56 closer to orifice 78 by the increased force transmitted by the fiyweights 64 and 66 as the engine speed is increased and by the increased pressure in chamber 36 caused by the increased flow of fuel into the downstream chamber 76 of the load sensor. When the forces transmitted by said yweights and the fuel in said chamber 36 once again balance the force transmitted in the opposite direction by the fuel in chamber 34, the flow of fuel through orifice 78 will be substantially linear to the speed of the engine and will correspond to the fiow of air into the intake manifold which air ow is also substantially linear to engine speed.

Referring to Figure 2, fuel injection nozzle 18 comprises a body 124 threadably received at 126 in manifold 88 and having a recess 128 in one end thereof frictionally receiving nozzle feed conduit 94. An orifice 130 and passage 132 in body 124 connects conduit 94 to manifold 88. An orifice restricting means or needle member 134 of any desirable cross sectional shape is reciprocably mounted in a bore 136 of complementary shape in body 124, said member having a tapered end 138 of complementary shape to orifice 130 and movable with respect thereto to regulate the pressure of the fuel in conduit 94. Attached to the end of member 134 is a flexible diaphragm 140 communicating on one side with the atmosphere through vent 142 and on the other side with a manifold pressure chamber 144 formed in body 124 and connected to manifold 88 through a fiuid passage 146. Spring 147 resiliently urges diaphragm 140 and attached member 134 away from orifice 130 with a force that is gradually overcome by an increasing vacuum in manifold 88. The protective housing section 148 is secured to body 124 by suitable means 150. A nut portion 152 integral with body 124 provides a convenient means for securing said body in the manifold.

In Figure 3 nozzle 18 is provided with a needle member 134 as in Figure 2 butthe end 154 of said needle is straight rather than tapered as in Figure 2 to provide only two operative positions for said needle throughout the total manifold pressure range of the engine. When the force of the manifold vacuum on diaphragm 140 is sufficient to overcome spring to bring end 154 of needle 134 into aperture or orifice 156 an orifice of constant size is created for all subsequent lower manifold pressures in contrast to Figure 2 wherein orifice 130 is variable in size over the manifold pressure range due to the tapered end 138 of needle 134. n

Also shown in Figure 3 is a variation in the manner of getting manifold pressure into chamber 144. This is accomplished by connecting a fluid conduit 158 to a pilot valve 160 rather than directly to the manifold as shown in Figure 2 by passages 146. The pilot valve 160 may be connected to a multiplicity of nozzles through a plurality of conduits 158 for use in a multicylinder engine. In the pilot valve, low manifold pressure is transmitted through passage 162 to chamber 164 to urge diaphragm 166 and pilot needle 168 to the left to connect bypass groove 170 to conduits 158. Manifold pressure passes through conduit 172, through bypass 178 and into chambers 144 of the nozzles to simultaneously adjust the nozzle orifice sizes. As the manifold pressure is in creased, pilot needle 168 will move to the right to cut off passage 172 and to connect conduits 158 to air bleed 174 and to simultaneously move all the nozzle needles to increase the size of the nozzle orifice. Diaphragm 166 is vented to the atmosphere through vent 176 and said diaphragm and the needle 168 connected thereto are resiliently urged to a bleed position by spring 178 the force of which is overcome by a predetermined vacuum in chamber 164. It is obvious that pilot valve 160 could also be used with the variable size orifice nozzle of Figure 2.

The function of nozzle 18 of Figure 2 is to varythe size or orifice 130 in proportion to the change in manifold pressure so as to maintain a substantially constant pressure drop across orifice 130. By maintaining a suficient pressure drop thereacross the vacuum in manifold 88 sucks enough fuel from conduits 94 to reduce the pressure of the fuel in said conduits to a point where vaporization will occur. At low engine speeds and loads the vacuum in manifold 88 would normally be high enough to suck a substantial portion of the fuel in conduit 94 and through orifice 130 or 156 and thereby sharply increase the vapor formation in conduit 94. By use of nozzle 18, however, the orifices 130 and 156 are greatly reduced in area during high manifold vacuum and sufficient fuel pressure in conduit 94 is maintained.

What is claimed is:

1. In a fuel injection system for a multicylinder internal combustion engine having an intake manifold, a plurality of fuel injection nozzles in said manifold, fuel feed means communicating with said nozzles, and means on said nozzles responsive to intake manifold pressure to automatically adjust the pressure drop across said nozzles as said manifold pressure varies to thereby maintain a relatively high fuel pressure in said fuel feed means at all operating manifold pressures. f l

2. In a fuel injection system for a n iulticylinder` internal combustion engine havingan intake manifold, arplural'ty of fuel injection nozzles in saidfmanifoldfuel feed means connecting saidY nozzles tol a fuel supply, a fnei orifice on each said nozzle disposed intermediate saidfuel feed means and said manifold, and adjustable pressure responsive valve means on said nozzles communicating with said manifold and responsive to pressure variations within said manifold to adjust the fuel pressuredrop across said orifices to maintain a relatively high fuel pressure in said fuelfeed means at all operating manifold pressures.

'3.l In afuel injection system for a multicylinder internal combustion engine having an intakey manifold, a plurality of'fuel injection nozzles in said manifold, fuel feedvmeans connecting saidnozzles to` a fuel supply, a fuel-orifice on each said nozzle communicating with said fuel feed means and said manifold, and adjustable pressure responsive valve means onsaid nozzles communicating with said manifold and responsive to pressure drops within said manifold to increase the fuel pressure d rop across said orificesv to maintain a relatively high fuel pressure said fuel feed means at all operating'` manifold pressures.

i 4. vIn a fuel injection system for multicylinder internalv combustion engines having an intake manifold, fuel iiijcctiony nozzles in said manifold'communicating'with sepa: rate cylinders of said engine, fuel feed means connecting saidk nozzles to a common fuel supply, fuel metering means in said fuel feed means adaptedvto regulate they quantity of fuel flowing to said nozzles according to engine fuel requirements and independently of the pressure drop across saidy nozzles, and means on said nozzles responsive to pressure variations within said intake manifold to adjust the pressure drop Vacross lsaid nozzlesr to maintain a relatively constant' high fuel pressure Within said'fuel feed means.

5. In a fuel injection system for internal" combustion engines having an intake manifold, a fuel injection nozzle insaid manifold communicating with said engine, fuel feed conduit means'connec'ting said" nozzle to va fuel supply, fuel metering means in said fuelv feed conduit means adapted to regulate the quantity of fuely flowing to said nozzle according to engine fuel requirements and independently of lthe pressure drop across said nozzle, and means on said nozzle responsive to pressure kdrops within said.l intake manifold to increase `thev pressure drop across said nozzle to maintain av relatively high fuel pressure within said fuelk feedy conduit means.

6.v In a fuel injection system for an'internal combustion engine having an intake manifold, a fuel injection nozzle vin said manifold, a fuel feed conduit connecting said nozzle tov a" fuel supply, fuel metering means in said conduit adapted to regulat'e'the quantity of' fuelv flowing to said nozzle according tol engine fuel requirements,

a fuel orifice on said nozzle connecting said fuel feed conduit to said manifold, and adjustable pressure responsivevalve means on said nozzle adjustable with respect to said orifice inV response to intake manifold pressure to adjust the pressure drop across said orifice to maintain a relatively high fuel pressure insaid fuel feed conduit. i

'7, In a fuel injection system for an internal combustion engine having an intake manifold, a fuel injection nozzle in said manifold, a fuel feed conduit connecting said nozzle to a fuel supply, fuel metering means in said conduit adapted to regulate the fiow of fuel to said nozzle according Vto engine fuel requirements, a fuel orifice on said nozzle'disposed intermediate said conduit and said manifold, and valve means on said nozzle communicating with said manifold and movable with respect to said orifice in response to manifold pressure to adjust the effective area ofsaid orifice to maintain relatively high fuel pressure in said conduit at all operating manifold pressures.

8. A fuel injection system for a multcylinder internal chamber and communicating with said separate manifold portions, and means. cooperating with said conduit means yfor maintaining` a relatively large fuel pressure drop from Said'cQnduit means to said manifold portions at all operating manifold pressures to maintain a relativelyv high fuel'pressure in said conduit means and said chamber' at alll said manifold pressures.

9;' In a Vfuel injection system for an internal combusf tion engine having an intake manifold, a fuel injection nozzle in said manifold, a fuel feed conduit connecting said nozzle to a fuel supply, fuel metering means'insaid v conduit adapted to regulate the roW of fuel to*- said nozzle according to engine fuel requirements, a fuel orifice on saidl nozzle disposed intermediate saidl conduit andsaid manifold, and valve means on said nozzle mov-. able with'fre'specttoV said orifice in response tointake manifold'pressure to maintain a relatively large fuel pressure. drop across saidwnozzle by adjusting the effective size of said orificeaccording to said manifold pressure, saidivalve means comprising a memberl shiftable into constricting relationship lwith said orifice, said, member being connected to a pressure responsive flexible diaphragm communicating with said manifold to receive pressuresigna-l's therefrom. Y A Y v 10. In a fuel injection system for an-internal com-bustion engine havingV an intake manifold, a fuel injection nozzle in said manifold, afuel feed conduit connecting said nozzle to-afuel supply, a fuel orifice on said nozzlekdisposed intermediate said conduit and said manifold, speed and load fuelV metering means in said conduit adapted tol regulate the ow of' fuel to said nozzle according-to engine speed and loadl fuel requirements kand independentlyfr of the pressure drop across said orifice, and valve means on said nozzle movable with respect to saidorifice in response' to intake manifold pressure to maintain a relatively large pressure drop across said orifice-.and to maintain relatively high lfuel pressure in saidf-uelf feed conduit at all operating manifold pressures', said-valve means'lcomprising a needle member shiftable intocons'tricting relationship with lsaid orifice, said miem"- ber being carried by-afiexible diaphragm, said diaphragm communicatingwith said manifold to receive' pressure signals therefrom and. being responsive thereto to move; with respect to said'orifice. Y'

1l'.- In a fuel injection system for an internal com-, bustion lengine having an intake manifold, affuelinjej,

cording to engine speed and load fuel requirements and independently of the pressure drop across said'orifice, valve means on said nozzleV movable with respect to said orificeV in response to intake manifold pressure yto maintain a relatively large pressure drop across said` orifice and to maintain relatively high fuell pressure in said fuel feed conduit at al1 operating manifold pressures, saidv valve meanscomprising a needle member shiftable into constricting relationship with said orifice, saidmemberA being carriedl by a flexible diaphragm, saidV diaphragm -communicating with said manifold to receive` pressurey signals therefrom and being responsive thereto to move with respect to said orifice, andresilient calibrated means: resiliently urging said diaphragm and said needle member away from said orifice.

l2. A fuel injection system for a multicylinder intern-aiA combustion engine, comprising an intake manifold havin g separate portions thereof communicating with separate cylinders of said engine, a fuel distribution cham;

n intake mani rold with sepa.A

ber communicating with a fuel source through a feed conduit, fuel metering means in said feed conduit adapted to meter fuel flowing to said chamber in accordance with engine operating parameters and the pressure of metered fuel, a plurality of fuel conduit means extending from said chamber and communicating with said separate manifold portions, and means associated with said conduit means for maintaining a relatively large fuel pressure drop from said conduit means to said manifold portions at all operating manifold pressures to maintain a relatively high fuel pressure in said conduit means, said chamber and said fuel metering means at all said manifold pressures, said fuel metering means being responsive to variations in said fuel pressure drop `to adjust the delivery of fuel to said distribution chamber.v

13. A fuel injection system for a multicylinder internal combustion engine, comprising an intake manifold having separate portions thereof communicating with separate cylinders of said engine, a fuel distribution chamber communicating with a fuel source through a feed conduit, speed and load fuel metering means connected to a drive portion and manifold portion of said engine respectively and operatively connected in said fuel feed conduit to meter fuel to said distribution chamber in accordance with engine speed and load, a plurality of fuel conduit means extending from said chamber and communicating with said separate manifold portions, and means on said conduit means for maintaining a relatively large fuel pressure drop from said conduit means to said manifold portions at all operating manifold pressures to maintain a relatively high fuel pressure in said conduit means, said chamber and said fuel metering means at all said manifold pressures, said fuel metering means being responsive to variations in said fuel pressure drop to adjust the fuel flow to said distribution chamber.

14. A fuel injection system for a multicylinder internal combustion engine having an intake manifold with separate portions thereof communicating with separate cylinders of said engine, comprising afuel distribution chamber communicating with a constant delivery fuel source, a plurality of fuel conduit means extending from said chamber and communicating with said separate mani fold portions, a fuel orifice on each said fuel conduit means adjacent each said manifold portion, and valve means on each said conduit means responsive to manifold pressure to adjust the effective area of each said orifice to maintain a relatively large fuel pressure drop from said conduit means to said manifold portions at all operating manifold pressures to maintain a relatively high fuel pressure in said conduit means and said cham- -ber at all said manifold pressures.

l5. In a fuel injection system for a multicylinder internal combustion engine having an intake manifold with separate branch portions communicating with separate cylinders of said engine, a fuel injection nozzle in each said manifold portion, fuel feed means connecting said nozzles to a fuel supply, a fuel orifice on each said nozzle defining a fluid connection between said fuel feed means and said manifold, a fuel distribution chamber in said fuel feed means for evenly distributing fuel to said nozzles, fuel metering means in said fuel feed means to regulate the flow of fuel to said chamber according to engine fuel requirements and independently of the pressure drop across said orifices, movable means on each said nozzle for adjusting the effective area of each said orifice in response to intake manifold pressure to maintain a relatively high pressure drop thereacross at all engine operating intake manifold pressures, each said movable means comprising a needle member carried by a pressure responsive iiexible diaphragm and shiftable into constricting relationship with each said orice, and pilot valve means communicating with said manifold and each of said diaphragms, said pilot valve means being responsive to manifold pressure to transmit said pressure simultaneously to each of said diaphragms to thereby cause a movement of each said needle member with respect to its associated orifice to maintain a relatively large fuel pressure drop across each said orifice at all operating manifold pressures for maintaining relatively high fuel pressures in said fuel feed means and said fuel distribution chamber at said manifold pressures.

16. In a fuel injection system foran internal combustion engine having an intake manifold, a fuel injection nozzle in said manifold, a fuel feed conduit connecting said nozzle to a constant delivery fuel supply, a return flow conduit connecting said fuel feed conduit to said fuel supply, speed metering means in said return flow conduit adapted to regulate the flow of fuel to said fuel supply in response to engine speed, a fuel orifice on said nozzle defining a tiuid connection between said fuel feed conduit and said manifold, and orifice restricting means slidably mounted in said nozzle, a movable diaphragm operatively connected to said restricting means, said diaphragm communicating with said manifold and responsive to pressures therein to move said orifice restricting means relative to said orifice to maintain relatively high fuel pressure in said fuel feed conduit at all operating manifold pressures by maintaining a relatively large pressure drop across said orifice.

17. In a fuel injection system for an internal combustion engine having an intake manifold, a fuel injection nozzle in said manifold, a fuel feed conduit connecting said nozzle to a constant delivery fuel supply, a return fiow conduit connecting said fuel feed conduit to said fuel supply, speed metering means in said return ow conduit operatively connected to a drive portion of said engine and adapted to regulate the flow of fuel to said fuel supply in response to engine speed, load metering means in said fuel feed conduit downstream of said speed metering means and being operatively connected to said manifold to regulate the liow of fuel to said nozzle in accordance with manifold pressure, a fuel orifice on said nozzle forming a uid connection between said fuel feed conduit and said manifold, orifice restricting means slidably mounted in said nozzle, a movable diaphragm operatively connected to said nozzle, said diaphragm communicating with said manifold and responsive to pressures therein to move said orifice restricting means relative to said orifice to maintain relatively high fuel pressure in said fuel feed conduit at all operating manifold pressures by maintaining a relatively large pressure drop across said orice. .f

18. In a fuel injection system for multicylinder internal combustion engines having an intake manifold with portions thereof communicating with the separate cylinders of said engine, a fuel injection nozzle in each said manifold portion, a fuel feed conduit connected to a constant delivery fuel supply, a fuel distribution chamber in said conduit, said chamber communicating with each said manifold portion, a return fiow conduit connecting said fuel feed conduit to said fuel supply, fuel metering means in said return flow conduit adapted to regulate the flow of fuel to said fuel supply, a fuel olifice on each said nozzle forming fluid connections between said chamber and said manifold portions, orifice restricting means slidably mounted in each said nozzle, each said restricting means being operatively connected to a separate movable diaphragm, each said diaphragm being connected to said manifold and responsive to intake manifold pressure to move said orifice restrictlng means relative to each said orifice to maintain relatively high fuel pressure in said chamber, said fuel feed conduit, and said fuel metering means at all operating manifold pressures by maintaining a relatively high fuel pressure drop across said orifice.

No references cited. 

